RF device with thermo-electric cooler

ABSTRACT

An RF device includes a support structure. An RF electrode is coupled to the support structure and includes conductive and dielectric portions. A thermo-electric cooler is coupled to the support structure and is configured to cool a back surface of the RF electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 10/072,475filed Feb. 6, 2002 now U.S. Pat. No. 7,022,121 and acontinuation-in-part of U.S. Ser. No. 10/072,610 filed Feb. 6, 2002 nowU.S. Pat. No. 7,141,049 both of which are continuations-in-part of U.S.Ser. No. 09/522,275, filed Mar. 9, 2000, now U.S. Pat. No. 6,413,255,which claims the benefit of U.S. Ser. No. 60/123,440, filed Mar. 9,1999. This application is also a continuation-in-part of U.S. Ser. No.10/026,870, filed Dec. 20, 2001, now U.S. Pat. No. 6,749,624, which is acontinuation of U.S. Ser. No. 09/337,015 filed Jun. 30, 1999, now U.S.Pat. No. 6,350,276, which is a continuation-in-part of U.S. Ser. No.08/583,815, filed Jan. 5, 1996, now U.S. Pat. No. 6,241,753, U.S. Ser.No. 08/827,237, filed Mar. 28, 1997, now U.S. Pat. No. 6,430,446, U.S.Ser. No. 08/914,681, filed Aug. 19, 1997, now U.S. Pat. No. 5,919,219,and U.S. Ser. No. 08/942,274, filed Sep. 30, 1997 now U.S. Pat. No.6,425,912, which are all fully incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates generally to the treatment of tissue, and moreparticularly to the treatment of skin surfaces.

DESCRIPTION OF RELATED ART

The human skin is composed of two elements: the epidermis and theunderlying dermis. The epidermis with the stratum corneum serves as abiological barrier to the environment. In the basilar layer of theepidermis, pigment-forming cells called melanocytes are present. Theyare the main determinants of skin color.

The underlying dermis provides the main structural support of the skin.It is composed mainly of an extra-cellular protein called collagen.Collagen is produced by fibroblasts and synthesized as a triple helixwith three polypeptide chains that are connected with heat labile andheat stable chemical bonds. When collagen-containing tissue is heated,alterations in the physical properties of this protein matrix occur at acharacteristic temperature. The structural transition of collagencontraction occurs at a specific “shrinkage” temperature. The shrinkageand remodeling of the collagen matrix with heat is the basis for thetechnology. Although the technology can be deployed to effect otherchanges to the skin, skin appendages (sweat glands, sebaceous glands,hair follicles, etc.), or subcutaneous tissue structures.

Collagen crosslinks are either intramolecular (covalent or hydrogenbond) or intermolecular (covalent or ionic bonds). The thermal cleavageof intramolecular hydrogen crosslinks is a scalar process that iscreated by the balance between cleavage events and relaxation events(reforming of hydrogen bonds). No external force is required for thisprocess to occur. As a result, intermolecular stress is created by thethermal cleavage of intramolecular hydrogen bonds. Essentially, thecontraction of the tertiary structure of the molecule creates theinitial intermolecular vector of contraction.

Collagen fibrils in a matrix exhibit a variety of spatial orientations.The matrix is lengthened if the sum of all vectors acts to lengthen thefibril. Contraction of the matrix is facilitated if the sum of allextrinsic vectors acts to shorten the fibril. Thermal disruption ofintramolecular hydrogen bonds and mechanical cleavage of intermolecularcrosslinks is also affected by relaxation events that restorepreexisting configurations. However, a permanent change of molecularlength will occur if crosslinks are reformed after lengthening orcontraction of the collagen fibril. The continuous application of anexternal mechanical force will increase the probability of crosslinksforming after lengthening or contraction of the fibril.

Hydrogen bond cleavage is a quantum mechanical event that requires athreshold of energy. The amount of (intramolecular) hydrogen bondcleavage required corresponds to the combined ionic and covalentintermolecular bond strengths within the collagen fibril. Until thisthreshold is reached, little or no change in the quaternary structure ofthe collagen fibril will occur. When the intermolecular stress isadequate, cleavage of the ionic and covalent bonds will occur.Typically, the intermolecular cleavage of ionic and covalent bonds willoccur with a ratcheting effect from the realignment of polar andnonpolar regions in the lengthened or contracted fibril.

Cleavage of collagen bonds also occurs at lower temperatures but at alower rate. Low-level thermal cleavage is frequently associated withrelaxation phenomena in which bonds are reformed without a net change inmolecular length. An external force that mechanically cleaves the fibrilwill reduce the probability of relaxation phenomena and provides a meansto lengthen or contract the collagen matrix at lower temperatures whilereducing the potential of surface ablation.

Soft tissue remodeling is a biophysical phenomenon that occurs atcellular and molecular levels. Molecular contraction or partialdenaturization of collagen involves the application of an energy source,which destabilizes the longitudinal axis of the molecule by cleaving theheat labile bonds of the triple helix. As a result, stress is created tobreak the intermolecular bonds of the matrix. This is essentially animmediate extra-cellular process, whereas cellular contraction requiresa lag period for the migration and multiplication of fibroblasts intothe wound as provided by the wound healing sequence. In higher developedanimal species, the wound healing response to injury involves an initialinflammatory process that subsequently leads to the deposition of scartissue.

The initial inflammatory response consists of the infiltration by whiteblood cells or leukocytes that dispose of cellular debris. Seventy-twohours later, proliferation of fibroblasts at the injured site occurs.These cells differentiate into contractile myofibroblasts, which are thesource of cellular soft tissue contraction. Following cellularcontraction, collagen is laid down as a static supporting matrix in thetightened soft tissue structure. The deposition and subsequentremodeling of this nascent scar matrix provides the means to alter theconsistency and geometry of soft tissue for aesthetic purposes.

In light of the preceding discussion, there are a number ofdermatological procedures that lend themselves to treatments whichdeliver thermal energy to the skin and underlying tissue to cause acontraction of collagen, and/or initiate a would healing response. Suchprocedures include skin remodeling/resurfacing, wrinkle removal, andtreatment of the sebaceous glands, hair follicles adipose tissue andspider veins.

Currently available technologies that deliver thermal energy to the skinand underlying tissue include Radio Frequency (RF), optical (laser) andother forms of electromagnetic energy as well as ultrasound and directheating with a hot surface. However, these technologies have a number oftechnical limitations and clinical issues which limit the effectivenessof the treatment and/or preclude treatment altogether.

These issues include the following: i) achieving a uniform thermaleffect across a large area of tissue, ii) controlling the depth of thethermal effect to target selected tissue and prevent unwanted thermaldamage to both target and non-target tissue, iii) reducing adversetissue effects such as burns, redness blistering, iv) replacing thepractice of delivery energy/treatment in a patchwork fashion with a morecontinuous delivery of treatment (e.g. by a sliding or painting motion),v) improving access to difficult-to-reach areas of the skin surface andvi) reducing procedure time and number of patient visits required tocomplete treatment. As will be discussed herein the current inventionprovides an apparatus for solving these and other limitations.

One of the key shortcomings of currently available RF technology fortreating the skin is the edge effect phenomenon. In general, when RFenergy is being applied or delivered to tissue through an electrodewhich is in contact with that tissue, the current concentrate around theedges of the electrode, sharp edges in particular. This effect isgenerally known as the edge effect. In the case of a circular discelectrode, the effect manifests as a higher current density around theperimeter of that circular disc and a relatively low current density inthe center. For a square-shaped electrode there is typically a highcurrent density around the entire perimeter, and an even higher currentdensity at the corners.

Edge effects cause problems in treating the skin for several reasons.First, they result in a non-uniform thermal effect over the electrodesurface. In various treatments of the skin, it is important to have auniform thermal effect over a relatively large surface area,particularly for dermatological treatments. Large in this case being onthe order of several square millimeters or even several squarecentimeters. In electrosurgical applications for cutting tissue, theretypically is a point type applicator designed with the goal of getting ahot spot at that point for cutting or even coagulating tissue. However,this point design is undesirable for creating a reasonably gentlethermal effect over a large surface area. What is needed is an electrodedesign to deliver uniform thermal energy to skin and underlying tissuewithout hot spots.

A uniform thermal effect is particularly important when cooling iscombined with heating in skin/tissue treatment procedure. As isdiscussed below, a non-uniform thermal pattern makes cooling of the skindifficult and hence the resulting treatment process as well. Whenheating the skin with RF energy, the tissue at the electrode surfacetends to be warmest with a decrease in temperature moving deeper intothe tissue. One approach to overcome this thermal gradient and create athermal effect at a set distance away from the electrode is to cool thelayers of skin that are in contact with the electrode. However, coolingof the skin is made difficult if there is a non-uniform heating pattern.

If the skin is sufficiently cooled such that there are no burns at thecorners of a square or rectangular electrode, or at the perimeter of acircular disc electrode, then there will probably be overcooling in thecenter and there won't be any significant thermal effect (i.e. tissueheating) under the center of the electrode. Contrarily, if the coolingeffect is decreased to the point where there is a good thermal effect inthe center of the electrode, then there probably will not be sufficientcooling to protect tissue in contact with the edges of the electrode.

As a result of these limitations, in the typical application of astandard electrode there is usually an area of non-uniform treatmentand/or burns on the skin surface. So uniformity of the heating patternis very important. It is particularly important in applications treatingskin where collagen-containing layers are heated to produce a collagencontraction response for tightening of the skin. For this and relatedapplications, if the collagen contraction and resulting skin tighteningeffect are non-uniform, then a medically undesirable result may occur.

There is a need for an improved devices for treating tissue sites. Thereis a further need for improved devices which provide cooling fortreating skin tissue.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide animproved RF device.

Another object of the present invention is to provide an RF device thatincludes an RF electrode with conductive and dielectric portions, and athermoelectric cooler.

Yet another object of the present invention is to provide a dielectricRF electrode coupled to a support member that is cooled by athermoelectric cooler

These and other objects of the present invention are achieved in an RFdevice that includes a support structure. An RF electrode is coupled tothe support structure and includes conductive and dielectric portions. Athermoelectric cooler is coupled to the support structure and isconfigured to cool a back surface of the RF electrode.

In another embodiment of the present invention, an RF device includes asupport structure coupled to an RF electrode. The RF electrode includesconductive and dielectric portions, and a flex circuit. A thermoelectriccooler is coupled to the support structure and is configured to cool aback surface of the RF electrode.

In another embodiment of the present invention, an RF device includes asupport structure coupled to an RF electrode. The RF electrode hasconductive and dielectric portions. A thermo-electric cooler is coupledto the support structure and is configured to cool a back surface of theRF electrode. First and second engagement members are formed in the bodyof the support structure. The first and second engagement membersprovide engagement and disengagement with a handpiece support structure.

In another embodiment of the present invention, an RE device includes asupport structure coupled to an RF electrode. The RF electrode has aconductive portion and is configured to be capacitively coupled with askin surface. A thermo-electric cooler is coupled to the supportstructure and is configured to cool a back surface of the RE electrode.A back plate is positioned at a proximal portion of the supportstructure. A plurality of electrical contact pads are coupled to theback plate.

In another embodiment of the present invention, an RF device includes asupport structure and an RF electrode with a conductive portion and aback surface. A back plate is positioned at a proximal portion of thesupport structure. The back plate includes a front surface that facesthe opposing back surface of the RF electrode and an opposing backsurface. A thermo-electric cooler is provided with distal section thatextends through the back plate and a proximal section that is raisedabove the back surface of the back plate.

In another embodiment of the present invention, an RF device Includes asupport structure coupled to the RF electrode. The RF electrode includesa conductive dielectric portion and a back surface. A thermoelectriccooler is coupled to the support structure. At least a first sensorcoupled to the RF electrode.

In another embodiment of the present invention, an RF device includes asupport structure coupled to an RF electrode. The RF electrode includesa conductive portion and a back surface. A thermo-electric cooler iscoupled to the support structure. A non-volatile memory coupled to theRF electrode.

In another embodiment of the present invention, an RF device includes asupport structure coupled to an RF electrode. The RF electrode hasconductive and dielectric portions. A thermoelectric cooler is coupledto the support structure and is configured to cool a back surface of theRF electrode. The thermoelectric cooler is distanced from the backsurface of the RF electrode.

In another embodiment of the present invention, an RF device includes asupport structure that defines a body of an RF device. An RF electrodeis provide with conductive and dielectric portions. The RF electrode isprovided with a flex circuit. A thermoelectric cooler is coupled to thesupport structure and is configured to cool a back surface of the RFelectrode.

In another embodiment of the present invention, an RF device includes asupport structure coupled to an RF electrode. The RF electrode includesconductive and dielectric portions. The RF electrode has a tissueinterface surface and an opposing back surface. A thermoelectric cooleris coupled to the support structure.

In another embodiment of the present invention, an RF device includes asupport structure coupled to an RF electrode. The RF electrodes includesconductive and dielectric portions, and has a tissue interface surfaceand an opposing back surface. The RF electrode has an outer edge with ageometry configured to reduce an amount of capacitively coupled area atthe outer edge. A thermo-electric cooler coupled to the supportstructure.

In another embodiment of the present invention, an RF device Includes asupport structure coupled to an RF electrode. The RF electrode includesconductive and dielectric portions, a tissue interface surface and anopposing back surface. At least a portion of the RF electrode has voidsthat reduce an amount of conductive material in the RF electrode. Athermo-electric cooler is coupled to the support structure.

In another embodiment of the present invention, an RF device includes asupport structure coupled to n RF electrode. The RF electrode hasconductive and dielectric portions. The RF electrode is configured toprovide a controllable tissue effect on subcutaneous tissue whilepreserving an epidermal skin surface overlying the subcutaneous tissue.A thermo-electric cooler is coupled to the support structure.

In another embodiment of the present invention, an RF device includes asupport structure coupled to an RF electrode. A flex circuit is coupledto the RF electrode. A thermoelectric cooler is coupled to the supportstructure.

In another embodiment of the present invention, an RF device includes asupport structure coupled to an RF electrode. A flex circuit is coupledto the RF electrode. A thermoelectric cooler is coupled to the supportstructure. A plurality of electrical contact pads are coupled to theflex circuit.

In another embodiment of the present invention, an RF device includes asupport structure coupled to an RF electrode. The RF electrode hasconductive and dielectric portions. A plurality of electrical contactpads are coupled to the RF electrode. A thermo-electric cooler iscoupled to the support structure.

In another embodiment of the present invention, an RF device includes asupport structure coupled to an RF electrode. The RF electrodes hasconductive and dielectric portions. At least portions of the RFelectrode have different widths. A thermoelectric cooler is coupled tothe support structure.

In another embodiment of the present invention, an RF device includes asupport structure coupled to an RF electrode. The RF electrode hasconductive and dielectric portions. At least portions of the RFelectrode has different conductivities. A thermo-electric cooler iscoupled to the support structure.

In another embodiment of the present invention, an RF device includes anRF electrode with conductive and dielectric portions. A supportstructure coupled to the RF electrode. The support structure and the RFelectrode form a seal where the support structure is coupled to the RFelectrode. A thermo-electric cooler is coupled to the support structure.

In another object of the present invention, an RF device includes an RFelectrode with including conductive and dielectric portions. A supportstructure is coupled to the RF electrode. A thermoelectric cooler iscoupled to the support structure and is configured to cool a backsurface of the RF electrode. The thermoelectric cooler is distanced fromthe back surface of the RF electrode. The support structure and the RFelectrode form a seal where the support structure is coupled to the RFelectrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a cross-sectional view of one embodiment of the handpieceof the present invention.

FIG. 1( b) is a cross-sectional view of another embodiment of the RFdevice with a thermoelectric cooler.

FIG. 2 is an exploded view of the FIG. 1 RF electrode assembly.

FIG. 3( a) is a close-up view of one embodiment of an RF electrode ofthe present invention.

FIG. 3( b) illustrates one embodiment of an RF electrode, that can beutilized with the present invention, with an outer edge geometryconfigured to reduce an amount of capacitively coupled area the outeredge.

FIG. 3( c) illustrates an one embodiment of an RF electrode, that can beutilized with the present invention, that has voids where there islittle if any conductive material.

FIG. 4 is a cross-sectional view of the RF electrode assembly from FIG.1.

FIG. 5 is a side view of one embodiment of an RF handpiece assembly ofthe present invention.

FIG. 6 is a rear view of the FIG. 5 RF electrode assembly.

DETAILED DESCRIPTION

In various embodiments, the present invention provides methods fortreating a tissue site. In one embodiment, an energy delivery surface ofan energy delivery device is coupled to a skin surface. The coupling canbe a direct, in contact, placement of the energy delivery surface of theenergy delivery on the skin surface, or distanced relationship betweenthe two with our without a media to conduct energy to the skin surfacefrom the energy delivery surface of the energy delivery device. The skinsurface is cooled sufficiently to create a reverse thermal gradientwhere a temperature of the skin surface is less than an underlyingtissue. Energy is delivered from the energy delivery device to theunderlying tissue area, resulting in a tissue effect at the skinsurface.

Referring now to FIG. 1( a), the methods of present invention can beachieved with the use of a handpiece 10. Handpiece 10 is coupled with ahandpiece assembly 12 that includes a handpiece housing 14 and a coolingfluidic medium valve member 16. Handpiece housing 14 is configured to becoupled to an electrode assembly 18. Electrode assembly 18 has a leastone RF electrode 20 that is capacitively coupled to a skin surface whenat least a portion of RF electrode 20 is in contact with the skinsurface. Without limiting the scope of the present invention, RFelectrode 20 can have a thickness in the range of 0.010 to 1.0 mm.

Handpiece 10 provides a more uniform thermal effect in tissue at aselected depth, while preventing or minimizing thermal damage to theskin surface and other non-target tissue. Handpiece 10 is coupled to anRF generator. RF electrode 20 can be operated either in mono-polar orbi-polar modes. Handpiece 10 is configured to reduce, or preferablyeliminate edge effects and hot spots. The result is an improvedaesthetic result/clinical outcome with an elimination/reduction inadverse effects and healing time.

A fluid delivery member 22 is coupled to cooling fluidic medium valvemember 16. Fluid delivery member 22 and cooling fluidic medium valvemember 16 collectively form a cooling fluidic medium dispensingassembly. Fluid delivery member 22 is configured to provide an atomizingdelivery of a cooling fluidic medium to RF electrode 20. The atomizingdelivery is a mist or fine spray. A phase transition, from liquid togas, of the cooling fluidic medium occurs when it hits the surface of RFelectrode 20. The transition from liquid to gas creates the cooling. Ifthe transition before the cooling fluidic medium hits RF electrode 20the cooling of RF electrode 20 will not be as effective.

In another embodiment, illustrated in FIG. 1( b), a thermoelectriccooler 23 is utilized in place of cooling fluidic medium valve member 16and fluid delivery member 22.

In one embodiment, the cooling fluidic medium is a cryogenic spray,commercially available from Honeywell, Morristown, N.J. A specificexample of a suitable cryogenic spray is R134A₂, available from Refron,Inc., 38-18 33^(rd) St, Long Island City, N.Y. 11101. The use of acryogenic cooling fluidic medium provides the capability to use a numberof different types of algorithms for skin treatment. For example, thecryogenic cooling fluidic medium can be applied milliseconds before andafter the delivery of RF energy to the desired tissue. This is achievedwith the use of cooling fluidic medium valve member 16 coupled to acryogen supply, including but not limited to a compressed gas canister.In various embodiments, cooling fluidic medium valve member 16 can becoupled to a computer control system and/or manually controlled by thephysician by means of a foot switch or similar device.

Providing a spray, or atomization, of cryogenic cooling fluidic mediumis particularly suitable because of it provides an availability toimplement rapid on and off control. Cryogenic cooling fluidic mediumallows more precise temporal control of the cooling process. This isbecause cooling only occurs when the refrigerant is sprayed and is in anevaporative state, the latter being a very fast short-lived event. Thus,cooling ceases rapidly after the cryogenic cooling fluidic medium isstopped. The overall effect is to confer very precise time on-offcontrol of cryogenic cooling fluidic medium.

Referring now to FIG. 2, fluid delivery member 22 and thermoelectriccooler 23 can be positioned in handpiece housing 14 or electrodeassembly 18. Fluid delivery member 22 is configured to controllablydeliver a cooling fluidic medium. Fluid delivery member 22 andthermoelectric cooler 23 cool a back surface 24 of RF electrode 20 andmaintain back surface 24 at a desired temperature. The cooling fluidicmedium evaporatively cools RF electrode 20 and maintains a substantiallyuniform temperature of front surface 26 of RF electrode 20. Fluiddelivery member 22 evaporatively cools back surface 24. Front surface 26may or may not be flexible and conformable to the skin, but it willstill have sufficient strength and/or structure to provide good thermalcoupling when pressed against the skin surface.

RF electrode 20 then conductively cools a skin surface that is adjacentto a front surface 26 of RF electrode 20. Suitable fluidic media includea variety of refrigerants such as R134A and freon.

Fluid delivery member 22 is configured to controllably deliver thecooling fluidic medium to back surface 24 at substantially anyorientation of front surface 26 relative to a direction of gravity. Ageometry and positioning of fluid delivery member 22 is selected toprovide a substantially uniform distribution of cooling fluidic mediumon back surface 24. The delivery of the cooling fluidic medium can be byspray of droplets or fine mist, flooding back surface 24, and the like.Cooling occurs at the interface of the cooling fluidic medium withatmosphere, which is where evaporation occurs. If there is a thick layerof fluid on back surface 24 the heat removed from the treated skin willneed to pass through the thick layer of cooling fluidic medium,increasing thermal resistance. To maximize cooling rates, it isdesirable to apply a very thin layer of cooling fluidic medium. If RFelectrode 20 is not horizontal, and if there is a thick layer of coolingfluidic medium, or if there are large drops of cooling fluidic medium onback surface 24, the cooling fluidic medium can run down the surface ofRF electrode 20 and pool at one edge or corner, causing uneven cooling.Therefore, it is desirable to apply a thin layer of cooling fluidicmedium with a fine spray. Thermo-electric cooler 23 achieves these sameresults but without delivering a cooling medium. Thermo-electric cooler23 is cold on the side that is adjacent to or in contact with surface24, while its opposing side becomes warmer.

In various embodiments, RF electrode 20, as illustrated in FIG. 3( a),has a conductive portion 28 and a dielectric portion 30. Conductiveportion 28 can be a metal including but not limited to copper, gold,silver, aluminum and the like. Dielectric portion 30 can be made of avariety of different materials including but not limited to polyimide,Teflon® and the like, silicon nitride, polysilanes, polysilazanes,polyimides, Kapton and other polymers, antenna dielectrics and otherdielectric materials well known in the art. Other dielectric materialsinclude but are not limited to polymers such as polyester, silicon,sapphire, diamond, zirconium-toughened alumina (ZTA), alumina and thelike. Dielectric portion 30 can be positioned around at least a portion,or the entirety of a periphery of conductive portion 28. In anotherembodiment, RF electrode 20 is made of a composite material, includingbut not limited to gold-plated copper, copper-polyimide,silicon/silicon-nitride and the like.

Dielectric portion 30 creates an increased impedance to the flow ofelectrical current through RF electrode 20. This increased impedancecauses current to travel a path straight down through conductive portion28 to the skin surface. Electric field edge effects, caused by aconcentration of current flowing out of the edges of RF electrode 20,are reduced.

Dielectric portion 30 produces a more uniform impedance through RFelectrode 20 and causes a more uniform current to flow throughconductive portion 28. The resulting effect minimizes or eveneliminates, edge effects around the edges of RF electrode 20. As shownin FIG. 3( c), RF electrode 20 can have voids 33 where there is littleor no conductive material. Creating voids 33 in the conductive materialalters the electric field. The specific configuration of voids can beused to minimize edge effect, or alter the depth, uniformity or shape ofthe electric field. Under a portion 28′ of the RF electrode 20 withsolid conductive material the electric field is deeper. Under a portion28″ of RF electrode 20 with more voids, the electric field is shallower.By combining different densities of conductive material, an RF electrode20 is provided to match the desired heating profile.

In one embodiment, conductive portion 28 adheres to dielectric portion30 which can be a substrate with a thickness, by way of example andwithout limitation, of about 0.001″. This embodiment is similar to astandard flex circuit board material commercially available in theelectronics industry. In this embodiment, dielectric portion 30 is incontact with the tissue, the skin, and conductive portion 28 isseparated from the skin.

The thickness of the dielectric portion 30 can be decreased by growingconductive portion 28 on dielectric portion 30 using a variety oftechniques, including but not limited to, sputtering, electrodeposition, chemical vapor deposition, plasma deposition and otherdeposition techniques known in the art. Additionally, these sameprocesses can be used to deposit dielectric portion 30 onto conductiveportion 28. In one embodiment dielectric portion 30 is an oxide layerwhich can be grown on conductive portion 28. An oxide layer has a lowthermal resistance and improves the cooling efficiency of the skincompared with many other dielectrics such as polymers.

In various embodiments, RF electrode 20 is configured to inhibit thecapacitive coupling to tissue along its outside edge 31. Referring toFIG. 3( b) RF electrode 20 can have an outer edge 31 with a geometrythat is configured to reduce an amount of capacitively coupled area atouter edge 31. Outer edge 31 can have less of the conductive portion 28material. This can be achieved by different geometries, including butnot limited to a scalloped geometry, and the like. The total length ofouter edge 31 can be increased, with different geometries, and the totalarea that is capacitively coupled to tissue is reduced. This produces areduction in energy generation around outer edge 31.

Alternatively, the dielectric material can be applied in a thicker layerat the edges, reducing the electric field at the edges. A furtheralternative is to configure the cooling to cool more aggressively at theedges to compensate for any electric field edge effect.

Fluid delivery member 22 has an inlet 32 and an outlet 34. Outlet 34 canhave a smaller cross-sectional area than a cross-sectional area of inlet32. In one embodiment, fluid delivery member 22 is a nozzle 36.

Cooling fluidic medium valve member 16 can be configured to provide apulsed delivery of the cooling fluidic medium. Pulsing the delivery ofcooling fluidic medium is a simple way to control the rate of coolingfluidic medium application. In one embodiment, cooling fluidic mediumvalve member 16 is a solenoid valve. An example of a suitable solenoidvalve is a solenoid pinch valve manufactured by the N-ResearchCorporation, West Caldwell, N.J. If the fluid is pressurized, thenopening of the valve results in fluid flow. If the fluid is maintainedat a constant pressure, then the flow rate is constant and a simpleopen/close solenoid valve can be used, the effective flow rate beingdetermined by the pulse duty cycle. A higher duty cycle, close to 100%increases cooling, while a lower duty cycle, closer to 0%, reducescooling. The duty cycle can be achieved by turning on the valve for ashort duration of time at a set frequency. The duration of the open timecan be 1 to 50 milliseconds or longer. The frequency of pulsing can be 1to 50 Hz or faster.

Alternatively, cooling fluidic medium flow rate can be controlled by ametering valve or controllable-rate pump such as a peristaltic pump. Oneadvantage of pulsing is that it is easy to control using simpleelectronics and control algorithms.

Electrode assembly 18 is sufficiently sealed so that the cooling fluidicmedium does not leak from back surface 24 onto a skin surface in contactwith a front surface of RF electrode 20. This helps provide an evenenergy delivery through the skin surface. In one embodiment, electrodeassembly 18, and more specifically RF electrode 20, has a geometry thatcreates a reservoir at back surface 24 to hold and gather coolingfluidic medium that has collected at back surface 24. Back surface 24can be formed with “hospital corners” to create this reservoir.Optionally, electrode assembly 18 includes a vent that permits vaporizedcooling fluidic medium to escape from electrode assembly 18.

The vent prevents pressure from building up in electrode assembly 18.The vent can be a pressure relief valve that is vented to the atmosphereor a vent line. When the cooling fluidic medium comes into contact withRF electrode 20 and evaporates, the resulting gas pressurizes the insideof electrode assembly 18. This can cause RF electrode 20 to partiallyinflate and bow out from front surface 26. The inflated RF electrode 20can enhance the thermal contact with the skin and also result in somedegree of conformance of RF electrode 20 to the skin surface. Anelectronic controller can be provided. The electronic controller sends asignal to open the vent when a programmed pressure has been reached.

Various leads 40 are coupled to RF electrode 20. One or more thermalsensors 42 are coupled to RF electrode. Suitable thermal sensors 42include but are not limited to thermocouples, thermistors, infraredphoto-emitters and a thermally sensitive diode. In one embodiment, athermal sensor 42 is positioned at each corner of RF electrode 20. Asufficient number of thermal sensors 42 are provided in order to acquiresufficient thermal data of the skin surface or the back surface 24 ofthe electrode 20. Thermal sensors 42 are electrically isolated from RFelectrode 20. In another embodiment, at least one sensor 42 ispositioned at back surface 24 of RF electrode and detects thetemperature of back surface 24 in response to the delivery of coolingfluidic medium.

Thermal sensors 42 measure temperature and can provide feedback formonitoring temperature of RF electrode 20 and/or the tissue duringtreatment. Thermal sensors 42 can be thermistors, thermocouples,thermally sensitive diodes, capacitors, inductors or other devices formeasuring temperature. Preferably, thermal sensors 42 provide electronicfeedback to a microprocessor of the RF generator coupled to RF electrode20 in order to facilitate control of the treatment.

Measurements from thermal sensors 42 can be used to help control therate of application of cooling fluidic medium. For example, a coolingcontrol algorithm can be used to apply cooling fluidic medium to RFelectrode 20 at a high flow rate until the temperature fell below atarget temperature, and then slow down or stop. A PID, orproportional-integral-differential, algorithm can be used to preciselycontrol RF electrode 20 temperature to a predetermined value.

Thermal sensors 42 can be positioned on back surface 24 of RF electrode20 away from the tissue. This configuration is preferable forcontrolling the temperature of the RF electrode 20. Alternatively,thermal sensors 42 can be positioned on front surface 26 of RF electrode10 in direct contact with the tissue. This embodiment can be moresuitable for monitoring tissue temperature. Algorithms are utilized withthermal sensors 42 to calculate a temperature profile of the treatedtissue. Thermal sensors 42 can be used to develop a temperature profileof the skin which is then used for process control purposes to assurethat the proper amounts of heating and cooling are delivered to achievea desired elevated deep tissue temperature while maintaining skin tissuelayers below a threshold temperature and avoid thermal injury.

The physician can use the measured temperature profile to assure that hestays within the boundary of an ideal/average profile for a given typeof treatment. Thermal sensors 42 can be used for additional purposes.When the temperature of thermal sensors 42 is monitored it is possibleto detect when RF electrode 20 is in contact with the skin surface. Thiscan be achieved by detecting a direct change in temperature when skincontact is made or examining the rate of change of temperature which isaffected by contact with the skin. Similarly, if there is more than onethermal sensor 42, the thermal sensors 42 can be used to detect whethera portion of RF electrode 20 is lifted or out of contact with skin. Thiscan be important because the current density (amperes per unit area)delivered to the skin can vary if the contact area changes. Inparticular, if part of the surface of RF electrode 20 is not in contactwith the skin, the resulting current density is higher than expected.

Referring again to FIG. 1( a), a force sensor 44 is also coupled toelectrode assembly 18. Force sensor 44 detects an amount of forceapplied by electrode assembly 18, via the physician, against an appliedskin surface. Force sensor 44 zeros out gravity effects of the weight ofelectrode assembly 18 in any orientation of front surface 26 of RFelectrode 20 relative to a direction of gravity. Additionally, forcesensor 44 provides an indication when RF electrode 20 is in contact witha skin surface. Force sensor 44 also provides a signal indicating that aforce applied by RF electrode 20 to a contacted skin surface is, (i)above a minimum threshold or (ii) below a maximum threshold.

As illustrated in FIG. 4, an activation button 46 is used in conjunctionwith the force sensor. Just prior to activating RF electrode 20, thephysician holds handpiece 10 in position just off the surface of theskin. The orientation of handpiece 10 can be any angle relative to thedirection of gravity. To arm handpiece 10, the physician can pressactivation button 46 which tares force sensor 44, by setting it to readzero. This cancels the force due to gravity in that particular treatmentorientation. This method allows consistent force application of RFelectrode 20 to the skin surface regardless of the angle of handpiece 10relative to the direction of gravity.

RF electrode 20 can be a flex circuit, which can include tracecomponents. Additionally, thermal sensor 42 and force sensor 44 can bepart of the flex circuit. Further, the flex circuit can include adielectric that forms a part of RF electrode 20.

Electrode assembly 18 can be moveably positioned within handpiecehousing 12. In one embodiment, electrode assembly 18 is slideablymoveable along a longitudinal axis of handpiece housing 12.

Electrode assembly 18 can be rotatably mounted in handpiece housing 12.Additionally, RF electrode 20 can be rotatably positioned in electrodeassembly 18. Electrode assembly 18 can be removably coupled to handpiecehousing 12 as a disposable or non-disposable RF device 52.

For purposes of this disclosure, electrode assembly 18 is the same as RFdevice 52. Once movably mounted to handpiece housing 12, RF device 52can be coupled to handpiece housing 12 via force sensor 44. Force sensor44 can be of the type that is capable of measuring both compressive andtensile forces. In other embodiments, force sensor 44 only measurescompressive forces, or only measures tensile forces.

RF device 52 can be spring-loaded with a spring 48. In one embodiment,spring 48 biases RF electrode 20 in a direction toward handpiece housing12. This pre-loads force sensor 44 and keeps RF device 52 pressedagainst force sensor 44. The pre-load force is tared when activationbutton 46 is pressed just prior to application of RF electrode 20 to theskin surface.

A shroud 50 is optionally coupled to handpiece 10. Shroud 50 serves tokeep the user from touching RF device 52 during use which can causeerroneous force readings.

A non-volatile memory 54 can be included with RF device 52.Additionally, non-volatile memory can be included with handpiece housing12. Non-volatile memory 54 can be an EPROM and the like. Additionally, asecond non-volatile memory can be included in handpiece housing 12 forpurposes of storing handpiece 10 information such as but not limited to,handpiece model number or version, handpiece software version, number ofRF applications that handpiece 10 has delivered, expiration date andmanufacture date. Handpiece housing 12 can also contain a microprocessor58 for purposes of acquiring and analyzing data from various sensors onhandpiece housing 12 or RF device 52 including but not limited tothermal sensors 42, force sensors 44, fluid pressure gauges, switches,buttons and the like.

Microprocessor 58 can also control components on handpiece 10 includingbut not limited to lights, LEDs, valves, pumps or other electroniccomponents. Microprocessor 58 can also communicate data to amicroprocessor of the RF generator.

Non-volatile memory 54 can store a variety of data that can facilitatecontrol and operation of handpiece 10 and its associated systemincluding but not limited to, (i) controlling the amount of currentdelivered by RF electrode 20, (ii) controlling the duty cycle of thefluid delivery member 22 and thermo-electric cooler 23, (iii)controlling the energy delivery duration time of the RF electrode 20,(iv) controlling the temperature of RF electrode 20 relative to a targettemperature, (v) providing a maximum number of firings of RF electrode20, (vi) providing a maximum allowed voltage that is deliverable by RFelectrode 20, (vii) providing a history of RF electrode 20 use, (viii)providing a controllable duty cycle to fluid delivery member 22 andthermo-electric cooler 23 for the delivery of the cooling fluidic mediumto back surface 24 of RF electrode 20, (ix) providing a controllabledelivery rate of cooling fluidic medium delivered from fluid deliverymember 22 to back surface 24, (x) providing a control of thermoelectriccooler 23 and the like.

Referring now to FIGS. 5 and 6, RE device 52 includes a supportstructure, including but not limited to a housing 60 that defines thebody of RE device 52. RE device 52 can include a back plate 62 that ispositioned at a proximal portion of support structure 60. A plurality ofelectrical contact pads 65 can be positioned at back plate 62. At leasta portion of fluid delivery member 22 and thermo-electric cooler 23 canextend through back plate 62. Fluid delivery member 22 can be a channelwith a proximal end that is raised above the back surface of back plate62.

First and second engagement members 64 can also be formed in the body ofsupport structure 60. Engagement members 64 provide engagement anddisengagement with handpiece housing 14. Suitable engagement members 64include but are not limited to snap members, apertures to engage withsnap members of substrate support 60, and the like.

Handpiece 10 can be used to deliver thermal energy to modify tissueincluding, but not limited to, collagen containing tissue, in theepidermal, dermal and subcutaneous tissue layers, including adiposetissue. The modification of the tissue includes modifying a physicalfeature of the tissue, a structure of the tissue or a physical propertyof the tissue. The modification can be achieved by delivering sufficientenergy to modify collagen containing tissue, cause collagen shrinkage,and/or a wound healing response including the deposition of new ornascent collagen, and the like.

Handpiece 10 can be utilized for performing a number of treatments ofthe skin and underlying tissue including but not limited to, (i) dermalremodeling and tightening, (ii) wrinkle reduction, (iii) elastosisreduction, (iv) scar reduction, (v) sebaceous gland removal/deactivationand reduction of activity of sebaceous gland, (vi) hair follicleremoval, (vii) adipose tissue remodeling/removal, (viii) spider veinremoval, (ix) modify contour irregularities of a skin surface, (x)create scar or nascent collagen, (xi) reduction of bacteria activity ofskin, (xii) reduction of skin pore size, (xiii) unclog skin pores andthe like.

In various embodiments, handpiece 10 can be utilized in a variety oftreatment processes, including but not limited to, (i) pre-cooling,before the delivery of energy to the tissue has begun, (ii) an on phaseor energy delivery phase in conjunction with cooling and (iii) postcooling after the delivery of energy to tissue has stopped.

Handpiece 10 can be used to pre-cool the surface layers of the targettissue so that when RF electrode 20 is in contact with the tissue, orprior to turning on the RF energy source, the superficial layers of thetarget tissue are already cooled. When RF energy source is turned on ordelivery of RF to the tissue otherwise begins, resulting in heating ofthe tissues, the tissue that has been cooled is protected from thermaleffects including thermal damage. The tissue that has not been cooledwill warm up to therapeutic temperatures resulting in the desiredtherapeutic effect.

Pre-cooling gives time for the thermal effects of cooling to propagatedown into the tissue. More specifically, pre-cooling allows theachievement of a desired tissue depth thermal profile, with a minimumdesired temperature being achieved at a selectable depth. The amount orduration of pre-cooling can be used to select the depth of the protectedzone of untreated tissue. Longer durations of pre-cooling produce adeeper protected zone and hence a deeper level in tissue for the startof the treatment zone. The opposite is true for shorter periods ofpre-cooling. The temperature of front surface 26 of RF electrode 20 alsoaffects the temperature profile. The colder the temperature of frontsurface 26, the faster and deeper the cooling, and vice verse.

Post-cooling can be important because it prevents and/or reduces heatdelivered to the deeper layers from conducting upward and heating themore superficial layers possibly to therapeutic or damaging temperaturerange even though external energy delivery to the tissue has ceased. Inorder to prevent this and related thermal phenomena, it can be desirableto maintain cooling of the treatment surface for a period of time afterapplication of the RF energy has ceased. In various embodiments, varyingamounts of post cooling can be combined with real-time cooling and/orpre-cooling.

In various embodiments, handpiece 10 can be used in a varied number ofpulse on-off type cooling sequences and algorithms may be employed. Inone embodiment, the treatment algorithm provides for pre-cooling of thetissue by starting a spray of cryogenic cooling fluidic medium, followedby a short pulse of RF energy into the tissue. In this embodiment, thespray of cryogenic cooling fluidic medium continues while the RF energyis delivered, and is stopping shortly thereafter, e.g. on the order ofmilliseconds. This or another treatment sequence can be repeated again.Thus in various embodiments, the treatment sequence can include a pulsedsequence of cooling on, heat, cooling off, cooling on, heat, cool off,and with cooling and heating durations on orders of tens ofmilliseconds. In these embodiments, every time the surface of the tissueof the skin is cooled, heat is removed from the skin surface. Cryogeniccooling fluidic medium spray duration, and intervals between sprays, canbe in the tens of milliseconds ranges, which allows surface coolingwhile still delivering the desired thermal effect into the deeper targettissue.

In various embodiments, the target tissue zone for therapy, also calledtherapeutic zone or thermal effect zone, can be at a tissue depth fromapproximately 100 μm beneath the surface of the skin down to as deep as10 millimeters, depending upon the type of treatment. For treatmentsinvolving collagen contraction, it can be desirable to cool both theepidermis and the superficial layers of the dermis of the skin that liesbeneath the epidermis, to a cooled depth range between 100 μm twomillimeters. Different treatment algorithms can incorporate differentamounts of pre-cooling, heating and post cooling phases in order toproduce a desired tissue effect at a desired depth.

Various duty cycles, on and off times, of cooling and heating areutilized depending on the type of treatment. The cooling and heatingduty cycles can be controlled and dynamically varied by an electroniccontrol system known in the art. Specifically the control system can beused to control cooling fluidic medium valve member 16 and the RF powersource.

The foregoing description of a preferred embodiment of the invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. Obviously, many modifications and variations will be apparentto practitioners skilled in this art. It is intended that the scope ofthe invention be defined by the following claims and their equivalents.

1. An RF device for non-invasively treating tissue using RF energy,comprising: a support structure; an RF electrode coupled to the supportstructure, the RF electrode including a dielectric portion and aconductive portion disposed on the dielectric portion, and thedielectric portion adapted to be positioned between the conductiveportion and a skin surface when the RF electrode is positioned at theskin surface, such that RF energy is capacitively coupled from theconductive portion into the tissue by transmission through thedielectric portion; and a thermo-electric cooler coupled to the supportstructure and configured to cool a back surface of the RF electrode. 2.The RF device of claim 1, wherein the thermo-electric cooler isconfigured to controllably cool the RF electrode.
 3. The RF device ofclaim 1, further comprising: a back plate positioned at a proximalportion of the support structure.
 4. The RF device of claim 3, furthercomprising: a plurality of electrical contact pads coupled to the backplate.
 5. The RF device of claim 3, wherein at least a portion of thethermo-electric cooler extends through the back plate.
 6. The RF deviceof claim 5, wherein the back plate has a back surface, and thethermo-electric cooler has a proximal end that is raised above the backsurface of the back plate.
 7. An RF device for non-invasively treatingtissue using RF energy, comprising: a support structure; an RF electrodecoupled to the support structure, the RF electrode including adielectric portion and a conductive portion disposed on the dielectricportion, and the dielectric portion adapted to be positioned between theconductive portion and a skin surface when the RF electrode ispositioned at the skin surface, such that RF energy is capacitivelycoupled from the conductive portion into the tissue by transmissionthrough the dielectric portion; a flex circuit coupled to the RFelectrode; and a plurality of electrical contact pads coupled to theflex circuit.
 8. An RF device for non-invasively treating tissue usingRF energy, comprising: a support structure; an RF electrode coupled tothe support structure and including a conductive portion and adielectric portion, the RF electrode configured to capacitively coupleRF energy with the tissue when at least a portion of the RF electrode isin contact with a skin surface, the conductive portion having voids, andthe dielectric portion adapted to be positioned between the conductiveportion and the skin surface when the RF electrode is positioned at theskin surface; and a flex circuit coupled to the RF electrode.
 9. The RFdevice of claim 8, further comprising: a back plate coupled to thesupport structure; and a plurality of electrical contact pads coupled tothe back plate.
 10. The RF device of claim 8, wherein the supportstructure includes first and second engagement members that provideengagement and disengagement with a handpiece support structure.
 11. TheRF device of claim 8, further comprising: a sensor coupled to the RFelectrode.
 12. The RF device of claim 11, wherein the RF electrode has aback surface, and the sensor is positioned at the back surface.
 13. TheRF device of claim 12, wherein the sensor detects a temperature of theback surface.
 14. The RF device of claim 8, further comprising: anon-volatile memory coupled to the RF electrode.